The Optimization Research For The Distillation System Of Acetone-butanol Based On Statistical Methods And Decoupling Algorithm

Acetone and bio-butanol were mainly produced by acetone-butanol-ethanol (ABE) fermentation process, which uses bacterial fermentation to produce acetone,1-butanol and ethanol from starch. The traditional four-column or five-column distillation process is still in use because the distillation system in the fermentation process is very complex and difficult to modify and optimize, with high energy consumption.In this thesis, the four-column distillation system was studied for the fermentation production of acetone-butanol. Considering the system's complexity, multi-parameters, severe coupling between streams, and non convergence during calculation, the whole distillation system was divided into three subsystems using the decoupling algorithm: prefractionator subsystem, butanol subsystem and ethanol acetone subsystem. And a mathematical model was built based on the subsystems. By using PRO/II process simulation software, the distillation system was simulated by analyzing the main components in the fermentation broth as well as their interactions, and then the mathematical model was modified based on the actual production data collected in a real factory.Through a detailed analysis of the simulation results, the distillation system deficiencies were found and a new process was proposed with the ultimate goal of energy saving and emission reduction. The new distillation process mainly included the side withdrawal technology, heat pump recovery process, reflow process, and comprehensive utilization of heat as well as a re-design of the butanol separator. Experimental data were collected in the prefractionator. Experimental data and simulated data agreed well, which proved the feasibility of the new process.One statistical method, response surface methodology (RSM), was introduced in order to optimize the new process completely. By minimizing the water content in the top or the solvent content in the bottom, many parameters were optimized together in the distillation system including prefractionator, 1#butanol column, and acetone column; mathematical models were built to correlate the factors and the objectives and then the optimized groups of parameters were obtained. Based on the obtained optimal parameters, PRO/â…¡process simulation software was reused to obtain the integrated optimal value. The results showed that the mathematical models were correct and the integrated optimized results were more accurate than the results from single-parameter optimization.In order to investigate the reliability of RSM optimization results, experimental data were obtained from the 1#butanol and acetone columns. The results agreed well with the integrated optimal values, which verified that RSM was reliable when used for multi-parameter optimization for the distillation system.The optimized new process has been applied in a project of energy-saving and consumption-reducing technological transformation. Run data and the calculated data agreed well. Compared to the traditional process, the effect of energy saving and consumption-reducing can reach 40% and 75% individually. That proved the advanced nature of this new technology and its reliability. The studies in this thesis provided a theoretical support on integrated optimization of the complex distillation system.